Benefits of Breastfeeding for Infants/Making an Informed
Decision
Breastfeeding is not a matter of choice, it is a public health matter, strongly stated the section on Breast- feeding of the American Academy of Pediatrics in its policy statement in 2012. The American College of Obstetrics and Gynecology (ACOG) has also signed on to this statement as has the American Academy of Family Practice (AAFP).
“The discussion is over, human milk is for human infants” proclaimed Myers at the twenty-fifth Sur- geon General’s Workshop in 2009. The evidence is overwhelming. The Old Testament states firmly that women should breastfeed their children. The Koran also indisputably commanded mothers to breastfeed their infants until they were 2 years old. Christians had been conspicuously silent until 1995 when Pope John Paul II spoke out and pro- claimed that the women of the world should breast- feed their children.
So why are we still discussing it? The evidence of the value of breastfeeding for both mother and child continues to mount. Along with the dozens of studies confirming what we already knew, there have been published challenging papers where the evidence is carefully culled to present a different picture. Studies analyzing the benefits have com- pared the “ever breastfed” to the formula-fed child.
Ever breastfed includes any infant who went to breast only once. The most challenging problem is setting up a controlled study randomly assigning women to breastfeed or including controls that were not to breastfeed; such a study is neither eth- ical nor possible. Formula feeding has been called the largest experiment in life with no science to
prove it is safe or efficacious. Formula is a necessary commodity only because not all women can or will breastfeed.
The evidence of the benefits of breastfeeding presented here is selected from the best of medical research. There has never been a study done that proves formula is better nor, in fact, even equal. For- mula is adequate when human milk is not available.
Compelling Reasons to Breastfeed
SPECIES SPECIFICITY
Species specificity encompasses all the benefits of being breastfed for human infants because breast milk is more than just good nutrition. Human breast milk is specific for the needs of human infants, just as the milk of thousands of other mammalian spe- cies is specifically designed for their offspring.
For optimal growth of brain and body, as well as protection against infection and development of immunity, human milk is specifically designed for all the needs of human infants.
NUTRITIONAL BENEFITS
Many benefits of breastfeeding are related to how children eat rather than what they eat as they get older. Breastfeeding eating is different from bottle- feeding, which depends on the maternal feeding style and her control of the process. The more fre- quently the infant bottle feeds (regardless of bottle 214
content) the more likely the mother focuses on giv- ing the infant enough. Mother encourages finishing every drop. This continues with later feeding habits to clean the plate and take more. This behavior is often the basic problem with obesity. In breastfeed- ing, the infant takes what he wants, no more. Feed- ing at the breast is a satisfying experience so that additional suckling is rarely needed.
The unique composition of breast milk provides the ideal nutrients for human brain growth, especially in the first year of life. Cholesterol, do- cosahexaenoic acid (DHA), and taurine are partic- ularly important. Cholesterol is part of the fat globule membrane and is present in approximately equal amounts in both cow milk and breast milk.
Maternal dietary intake of cholesterol has no impact on breast milk’s cholesterol content. Formula natu- rally lacks human DHA and taurine. The choles- terol in cow milk, however, has been removed in infant formulas, which are cholesterol-free. These elements—cholesterol, DHA, and taurine—are readily available from breast milk and are essential nutrients for human infants, especially for growth of the brain. Regardless of what additives are man- ufactured and added to bovine formula, they all have their origin from some other species and have been chemically extracted and subjected to exten- sive heat.
The maximum bioavailability of essential nutri- ents, including micro minerals, means that digestion and absorption are highly efficient. Comparison of the biochemical percentages of constituents of breast milk and infant formula fails to reflect the highly efficient bioavailability and utilization of constituents in breast milk compared with modified cow milk, from which only a small fraction of some nutrients is absorbed.
Nourishment with breast milk is a combination event, in which nutrient-to-nutrient interaction is significant. The process of mixing isolated single nutrients in formula does not guarantee the nutrient or nonnutrient benefits that result from breastfeed- ing. The composition of human milk is a delicate balance of macronutrients and micronutrients, each in the proper proportion to enhance absorption.
Ligands bind to some micronutrients to enhance their absorption. Enzymes also contribute to the digestion and absorption of all nutrients. All enzymes and hormones have been destroyed by processing in infant formulas.
An excellent example of balance is the action of lactoferrin, which binds iron to make it unavailable for Escherichia coli, which depends on iron for growth. When the iron is bound, E. coli cannot flourish and the normal flora of the newborn gut, Lactobacillus bifidus (Bifidobacterium bifidum), can thrive.
In addition, the small amount of iron in human milk is almost totally absorbed, whereas only about 10%
of the iron in formula is absorbed by the infant.
Nutrients such as proteins are examples of constit- uents in human milk with multiple functions, which include preventing infection and inflammation, promoting growth, transporting micro minerals, catalyzing reactions, and synthesizing nutrients.93 IMPACT ON CARDIOVASCULAR
HEALTH
A study asking the question of whether perinatal supplementation of long-chain polyunsaturated fatty acids prevents hypertension in later life con- cluded that long-chain polyunsaturated fatty acids depended upon other nutrients as well. Thus it was concluded that breastfeeding the infant can protect against insulin resistance and hypertension in later life.18A meta-analysis by Martin et al.58involving 15 studies and 17,503 subjects revealed that a small reduction in diastolic blood pressure was associated with breastfeeding, which confers long-term bene- fits on cardiovascular health. Another study by Martin et al.59reported a reduced risk for athero- sclerosis by breastfeeding as recorded in the 65- year follow-up of the Boyd Orr Cohort. The Boyd Orr Cohort is an historical cohort based on the Carnegie Survey diet and health in prewar Britain 1937 to 1939. This cohort involves 4999 partici- pants of 1343 families in 16 centers in England and Scotland who participated in a 1-week diet sur- vey when 0 to 19 years old between 1937 and 1939.
The trace rate was 88 when they were sent follow- up surveys. In 2002, 2563 of the original cohort were alive and living in Britain. Controlling for numerous variables, socioeconomic status, smok- ing, and alcohol made little difference.57 A pro- spective cohort study of 2512 men between 45 and 59 years of age were studied according to their infant feeding history. There was a positive associ- ation between breastfeeding and coronary heart disease mortality and incidence. There was no evi- dence of a duration-response effect. Breastfeeding was not associated with stature, blood pressure, insulin resistance, total cholesterol (TC), or fibrin- ogen. These data, however, only compared ever breastfed and bottle fed. Small studies of exclu- sively breastfed infants have shown breastfeeding impacts blood pressure. Large studies use all sub- jects if ever breastfed and the significance is muted. Studies of TC and low-density lipoprotein (LDL) cholesterol showed that levels were higher in infants while consuming breast milk which contains cholesterol. (Formula contains no choles- terol.) Levels in adult life are lower in breastfed infants suggesting that breastfeeding has long-term benefits for cardiovascular health.74Adult glucose tolerance tests showed lower 120 minute glucose levels in -individuals who had been breastfed.79
In this same Boyd Orr Cohort, Martin et al.59 studied the impact of breastfeeding and social mobility after 60 years. Prevalence of breastfeeding varied from 45% to 86% by district but not with household income, number of siblings, birth order, or social class in childhood. Breastfeeding was asso- ciated with upward social mobility; the longer the duration, the greater the probability, an effect that was not explained by other factors. Childhood obesity and infant feeding has also been evaluated by systematic review of published studies on Med- line since 1966.74,35,36 In 28 studies involving 298,900 subjects providing odds ratios, breastfeed- ing was associated with a reduced risk for obesity compared to formula-fed infants. Even in six studies adjusted for parental obesity, maternal smoking, and social class the effect was reduced but present.
For decades, growth in infancy had been mea- sured according to data collected on infants who were exclusively formula fed, until the publication of data in the 1990s on the growth curves of infants who were exclusively breastfed.25 The physiologic growth curves of breastfed infants show a pattern similar to that of formula-fed infants at the 50th per- centile, with significantly fewer breastfed infants in the 90th percentile. This is most evident in the examination of the Z-scores, which indicate that formula-fed infants are heavier compared with breastfed infants, meaning that more are obese.25,24 The World Health Organization (WHO) con- structed an international study involving seven coun- tries, rich and poor, to record how children should grow.101All participants were exclusively breastfed and had good health. The growth curves from these observations are available worldwide and should replace old curves that demonstrate how children grow, the tall and the short, the fat and the thin, the sick and well. These old curves which included all children are mathematical averages of the good and bad. These growth issues are discussed more completely inChapter 11.
A study of adolescents, assessing body composi- tion including height, weight, skinfolds, and waist circumferences, showed an effect of being breastfed if “never breastfed” was compared to breastfed over 4 months in a European multicentered study.
Breastfeeding for at least 1 year or more had a pro- found effect on the development of obesity in Hispanic toddlers. Breastfeeding in this group was associated with a reduced intake of sugar- sweetened beverages.20,83
INFECTION PROTECTION
Leukocytes, specific antibodies, and other antimi- crobial factors protect breastfed infants against many common infections. Protection against
gastrointestinal infections is well documented.36Pro- tection against infections of the upper and lower respiratory system and the urinary tract is less recog- nized but equally well documented. These infections lead to more emergency room visits, hospitalizations, treatments with antibiotics, and health care costs for the infant who is not breastfed.2
The incidence of acute lower respiratory infec- tions in infants has been evaluated in a number of studies examining the relationship between respira- tory infections and breastfeeding or formula feed- ing in these infants.77These studies confirm that breastfed infants are less likely to be hospitalized for respiratory infection and, if hospitalized, are less seriously ill.11In a study of infant deaths from infectious disease in Brazil, the risk for death from diarrhea was 14 times more frequent in formula-fed infants, and the risk for death from respiratory ill- ness was 4 times more frequent.
According to the report from the Agency for Health Research Quality (AHRQ) in 2007,36 breastfeeding for 4 or more months is associated with a reduction in the risk for hospitalization sec- ondary to lower respiratory tract disease.
The association of wheezing and allergy with infant feeding patterns has also shown a significant advantage to breastfeeding. In a report from a 7-year prospective study in South Wales, the advantage of breastfeeding persisted to age 7 years in nonatopic infants, and in at-risk infants who were breastfed the risk for wheezing was 50% lower (after accounting for employment status, passive smoking, and overcrowding).10 Breastfeeding is thought to confer long-term protection against respiratory infection as well.
Upper and lower respiratory tract infections have been evaluated in case-control studies, cohort-based studies, and mortality studies in both clinic attended and hospitalized children in many countries of the developed world.20,15,52 The results show clearly that breastfeeding has a pro- tective effect, especially in the first 6 months of life. Acute respiratory infections (ARIs) were studied by Vereen et al. because they are a major cause of infant morbidity. Ever breastfed were compared with never breastfed in a cross-sectional analysis of viral severity in 629 mother-infant dyads. When the infant had ARI, breastfeeding was associated with a decreased risk of having lower versus upper respira- tory tract infection. A randomized, controlled trial indicated that withholding cow milk and giving soy milk provided no such protective effect.12The inci- dence of acute otitis media in formula-fed infants is dramatically higher than in breastfed infants,1,3not only because of the protective constituents of human milk but also because of the process of suckling at the breast, which protects the inner ear. When an infant
feeds by bottle, the eustachian tube does not close, and formula and secretions are regurgitated in the tubes. Child care exposure increases the risk for otitis media, and bottle-feeding amplifies this risk.15,52The longer the breastfeeding, the more prolonged the protection.36
IMMUNOLOGIC PROTECTION
In addition to the protection provided by breastfeed- ing against acute infections, epidemiologic studies have revealed a reduced incidence of childhood lym- phoma,21both acute lymphocytic and acute myelog- enous leukemia,36,5,48and type 1 insulin-dependent diabetes,96as well as type 2 diabetes and Crohn dis- ease,45in infants who have been exclusively breastfed for at least 4 months, compared with formula-fed infants. In a systematic review and meta-analysis of breastfeeding and childhood cancer published in 49 references between 1966 and 2004, the authors report lower risks such as decreased incidence of acute lym- phoblastic leukemia, Hodgkin’s disease, and neuro- blastoma. These findings were based on “ever breastfed,” not inclusive breastfeeding for 6 months.60 Within this cohort, a meta-analysis by Kwan et al.49 strongly supported the impact of breastfeeding on limiting the risk of childhood leukemia. It demon- strated that longer breastfeeding reduced the risk.
ALLERGY PROPHYLAXIS
Breastfed infants at high risk for developing allergic symptoms such as eczema and asthma by 2 years of age show a reduced incidence and severity of symp- toms in early life.10Some studies suggest the pro- tective effect continues through childhood.9,43 A significant reduction in risk for childhood asthma at age 6 years was reported by Oddy et al.72 if exclusive breastfeeding is continued for at least 4 months. Available evidence regarding full-term infants in developed countries suggests that exclu- sive breastfeeding for at least 3 months is associated with a reduced risk for atopic dermatitis in children with a family history of atopy.30
Prolonged breastfeeding may improve subse- quent lung function at 10 years old. Forced vital capacity, forced expiratory volume, and peak expi- ratory flow were measured in 1456 children who were part of the Isle of Wight Study; 196 were not breastfed, 243 were breastfed less than 2 months, 142 were breastfed more than 2 months but less than 4 months, and 374 were breastfed at least 4 months. Lung volume was enhanced in the breastfed children. The authors4 speculate that the effect on airflow was mediated by lung volume changes, which could be the result of prolonged
suckling at the breast, providing a mechanical stim- ulus to improve the mechanics of ventilation.4
PSYCHOLOGICAL AND COGNITIVE BENEFITS
The prevailing impression from large epidemiolog- ical studies is that being breastfed results in higher cognitive function and higher performance intel- lectually. Does breastfeeding alter early brain development? Morphometric brain imaging has supported this premise.23 Increased white matter and subcortical gray matter volume and parietal lobe cortical thickness have been observed. When quiet magnetic resonance imaging (MRI) scans were used to compare measurements of white mat- ter microstructure in 133 healthy children aged 10 months through 4 years who were exclusively breastfed a minimum of 3 months with those for- mula fed or fed a mixture, the breastfed children had increased white matter in frontal and associated brain regions. Other regions were anatomically consistent with improvements in cognitive and behavior performance measures. The developmen- tal advantages associated with breastfeeding are supported by the hypothesis that breastfeeding promotes healthy neural growth and white matter development, according to investigators.23
Nielsen and O’Hara71noted that children who had been breastfed were more mature, secure, and assertive, and they progressed farther on the developmental scale than nonbreastfed children.
More recently, studies by Lucas et al.56and other investigators38 found that premature infants who received breast milk provided by tube feeding were more advanced developmentally at 18 months and at 7 to 8 years of age than those of comparable ges- tational age and birth weight children who had received formula by tube. Such observations sug- gest that breast milk has a significant impact on the growth of the central nervous system. This sug- gestion is further supported by studies of visual activity in premature infants who were fed breast milk compared with those who were fed infant for- mula. When similar studies were performed in full- term infants, visual acuity developed more rapidly in the breastfed infants.40 Even when DHA was added to formula, the performance by breastfed infants was still better.39
An 18-year longitudinal study reported by Horwood and Fergusson33 demonstrates a small but detectable increase in childhood cognitive and educational achievement in infants who were breastfed. The effects were confirmed in a range of measures, including standardized tests, teacher ratings, and academic outcomes in high school
and young adulthood. More than 1000 children in New Zealand participated. Children who were breastfed for 8 months or longer had a mean test score at age 18 that was 0.11 to 0.30 standard devi- ation units higher than those not breastfed.
To examine the association between duration of infant breastfeeding and intelligence in young adult life, Mortensen et al.68 conducted a prospective longitudinal cohort study of more than 3000 indi- viduals in Denmark born between 1959 and 1961. They concluded that, independent of a wide range of possible confounding factors, a significant positive association between duration of breast- feeding and intelligence test results existed, using two separate intelligence tests.
In an effort to examine the minimum duration of exclusive breastfeeding for optimal neurologic out- come, Bouwstra et al.6assessed the quality of gen- eral movements at 3 months of 147 breastfeeding, healthy term infants. General movement quality is considered a sensitive marker of neurologic status according to the authors. They demonstrated a positive effect between breastfeeding duration and general movement quality with a saturation effect at about 6 weeks. They concluded that exclu- sive breastfeeding for at least 6 weeks might improve neurologic outcome.
Evidence-Based Systematic Reviews
In 2007, two careful, comprehensive assessments of the value of human milk and breastfeeding were published: one from the AHRQ,36the other from the Department of Child and Adolescent Health and Development of WHO. The AHRQ reviewed the evidence on the effects of short- and long-term breastfeeding on infants and maternal health out- comes in developed countries. More than 9000 abstracts were screened and 400 individual studies reviewed. The data supported a long list of advan- tages (Tables 7-1and7-2) but did not support the increase in cognitive performance. The relation- ship between breastfeeding and cardiovascular dis- ease was unclear. Maternal risk reduction is noted inTable 7-3, and only weight loss and osteoporo- sis reduction was unclear from the studies. The authors did comment that breastfeeding did not mean exclusive breastfeeding.36 The Irish Nursing Homes Organization (INHO) analysis also reflected a lack of clarity in terms of impact on intellectual performance, cardiovascular disease, and obesity.61 When the analysis was complete, however, they were able to confirm that long-term subjects who were breastfeeding experienced lower mean blood pressure and TC and higher perfor- mance on intelligence tests. The prevalence of overweight and obesity and type 2 diabetes was lower among breastfeeding infants. Although all
were statistically significant some differences were modest. The definition of breastfeeding, exclusive or partial, and length of breastfeeding remain sig- nificant factors in measuring outcome.
Since these two meta-analyses were performed, several new studies have been published that fur- ther support advancement in intellectual skills.51
TABLE 7-1 Advantages of Breastfeeding as Determined by AHRQ Full-Term Infant
Outcomes Reduction in Relative Risk Acute otitis media 50% reduction
Atopic dermatitis Equivocal Gastrointestinal
infections
64% reduction Lower respiratory
tract disease 72% reduction
Asthma 27% reduction
Cognitive
development Equivocal because of confounding factors
Obesity 24%, 7%, 4% for each month of breastfeeding
Risk for cardiovascular disease
Blood pressure: up to 1.5 monthly reduction; LDL cholesterol:
7.0–7.7 mg/dL reduction; all- cause CV mortality: needs further investigation
Type 2 diabetes 39% reduction (confounders not well controlled)
Childhood
leukemias 19% reduction (all); 15% (AML)
SIDS 36% reduction
AHRQ,Agency for Health Research Quality;AML,acute myelogenous leukemiaCV,cardiovascular;LDL,low- density lipoprotein;SIDS,sudden infant death syndrome.
Summarized from AHRQ report no. 15335,36.
TABLE 7-2 Maternal Advantages of Breastfeeding as Determined by AHRQ
Mother Outcomes Reduction in Relative Risk Return to
prepregnancy weight
Unclear
Maternal type 2 diabetes
2%-12%
Osteoporosis Unclear Postpartum
depression Too few studies
Breast cancer 28% for 12 or more months (4.3%
for each year of breastfeeding) Ovarian cancer 21%
Intensity and duration of breastfeeding were not defined in most studies, thus diluting the magnitude of the effects.44
AHRQ,Agency for Health Research Quality.